The aim of the proposed research is to assess the sensitivity of the latency of the P1 cortical auditory evoked potential as a marker of the development of the central auditory pathways in hearing impaired children who receive intervention through conventional hearing aids, multichannel cochlear implants, or a combination of the two technologies. In a series of 10 experiments we propose to (1) collect age norms for P1 latency in normal hearing infants and children, (2) assess the relationship between P1 latency, degree of hearing loss and speech perception performance in children with varying degrees of hearing loss, (3) conduct longitudinal assessment of P1 latency in hearing-impaired infants who are provided with amplification as an initial intervention, (4) determine whether electrical stimulation from multichannel cochlear implants produces decreases in P1 latencies that were not seen previously with acoustic amplification and (5) cross-validate electrophysiological measures (P1 latencies) to measures of early communicative behavior in order to determine if P1 latencies are an adequate predictor for the initiation of speech and language development following hearing intervention via hearing aids or cochlear implants. Our goal is to provide clinicians with an objective tool to evaluate whether acoustic amplification for hearing impaired children has provided sufficient stimulation for normal development of the central auditory pathways. If clinicians have such a marker, then they can more confidently make a decision about whether to provide a child with a cochlear implant following an appropriate hearing-aid trial. Using the same marker, clinicians will also be able to monitor the maturation of central auditory pathways once electrical stimulation is initiated.